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package com.google.jgments;

import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.io.Resources;
import com.google.jgments.syntax.LanguageDefinition;
import com.google.jgments.syntax.PythonSyntax;

import java.io.IOException;
import java.nio.charset.Charset;

import javax.annotation.Nullable;

/**
 * A lexer based on regular expressions and state transitions.
 * This is a port of the corresponding class from Pygments.
 */
public class RegexLexer implements Iterable<SyntaxSpan> {
  private final LanguageDefinition lang;
  private final String text;
  private final LexerState state;

  public RegexLexer(LanguageDefinition lang, String text) {
    this(lang, text, null);
  }

  public RegexLexer(LanguageDefinition lang, String text, @Nullable LexerState state) {
    this.lang = checkNotNull(lang);
    this.text = checkNotNull(text);
    this.state = state;
  }

  public RegexLexerIterator iterator() {
    return new RegexLexerIterator(lang, text, state);
  }

  /** Sample method for exercising RegexLexer. */
  public static void main(String[] argv) throws IOException {
    String text = Resources.toString(
        RegexLexer.class.getResource("extract.py"), Charset.defaultCharset());
    RegexLexer lexer = new RegexLexer(PythonSyntax.INSTANCE, text);
    for (SyntaxSpan annotation : lexer) {
      System.out.println(annotation);
    }
  }
}
